1. Technical Field
This invention relates to dynamoelectric machines and, more particularly, to an apparatus for biasing a brush of the machine towards an operative position. Additionally, the invention relates to a method for assembling a brush holder assembly to thus ease the assembly procedure.
2. Discussion
Brush riggings for motors and generators and the like vary in design, but in general consist of boxes to house the brushes, a spring means to apply pressure to the brushes to urge them against a commutator, connecting electrical leads to provide a current path to the brushes and a mounting surface to secure these elements to. The mounting surface also serves to provide some means to secure the entire assembly to the motor in such a manner as to place the brushes in a proper working relationship with the commutator. One of the most popular designs, especially for small fractional horsepower motors such as that disclosed in commonly assigned U.S. Pat. No. 4,694,214, which is hereby incorporated by reference, utilizes a molded brush card member of a one-piece construction formed from a high temperature resistant plastic which is electrically non-conductive. The member has the brush boxes formed thereon as well as various openings for securing it to the motor housing and for receiving an extending armature shaft and the commutator secured to the shaft.
Each of the brush boxes defines a cavity for receiving a brush and positioning the brush for reciprocating motion inwardly and outwardly. A length of conductive wire, commonly termed a "brush shunt", extends outwardly from the outboard end of the brush and terminates at a disk-like terminal cap. A coil spring is disposed about the brush shunt to extend between the terminal cap and the outboard end of the brush for urging the brush inwardly. A conductor is mounted to the terminal cap to conduct current to the motor as desired.
Although such a brush card arrangement has proven very satisfactory in operation, it is laborious to assemble the brushes into the brush card. This is because the coil spring must be compressed nearly to its "stacked" height and so held while the brush shunt is passed through the central hollow of the coil spring and then mounted to its terminal cap. Additionally, to replace a worn brush, the motor end cap must be removed to provide access to the brush card.
Accordingly, it is a principal object of the present invention to provide a brush holder assembly for a dynamoelectric machine wherein the brush shunt may be mounted to an electrically conductive terminal without the necessity of first compressing the brush spring.
It is another aspect of the present invention to provide an end cap which includes a brush housing for holding the brush holder assembly of the present invention whereby the brush holder assembly may be accessed without removing the motor end cap from the dynamoelectric machine.
It is yet another object of the present invention to provide a novel method of assembly of a brush holder whereby the brush holder assembly can be assembled without first compressing a coil spring associated therewith.
It is still another object of the present invention to provide an apparatus for biasing a brush outwardly of a brush box, and a method for assembling same without first compressing the biasing member, which does not require the use of any special components or especially constructed tools.